This legally binding international treaty has now been ratified by 196 states (including Sri Lanka) as well as the European Union. With such universal ratification, it is the world’s most widely subscribed international law.

It is an extraordinary success story of governments, experts and ordinary people coming together and acting resolutely to protect all life on Earth from the Sun’s harmful ultraviolet rays.

In a quarter century, it has rallied governments and industries in both developed and developing countries to phase out, or substantially reduce, nearly 100 chemicals that damage the ozone layer in the upper atmosphere.

A landmark was reached at the end of 2009, when the production and use of chlorofluorocarbons (CFCs) – widely used in refrigerators and air-conditioners – was totally phased out.

If this treaty was not in place, the ozone layer would have continued to deplete and been about 10 times worse than current levels. By halting and then gradually reversing ozone loss, the treaty is estimated to have prevented some 19 million cases of non-melanoma (skin) cancer, 1.5 million cases of melanoma cancer and 130 million cases of eye cataracts.

This doesn’t count many other hazards of ozone depletion to the world’s plant and animal life, entire ecosystems and the oceans.

Ozone Safe World

But catastrophe was averted just in time. Recent global measurements show the ozone layer is naturally healing. If current trends continue, and all controlled chemicals are phased out on schedule without any backsliding, the ozone layer is expected to be restored to its pre-1980s levels by around 2070.

The credit for this achievement in intergovernmental cooperation is widely shared. It was possible thanks to the passion, dedication and hard work of many individuals in government, corporate, academic, civil society sectors. Their combined efforts literally helped save our sky.

The Montreal Protocol is now hailed as a classic case of evidence-based policy making and concerted action to protect a global commons. The officials, diplomats, industry leaders and technical experts who negotiated the 1987 Protocol built on cutting edge scientific research.

In fact, scientists were concerned about the ozone layer from the early 1970s. It was on the agenda for the 1972 Stockholm Conference on the Human Environment, but high-flying supersonic aircraft were seen then as the main threat. (Aviation, even then, was an easy target!).

F Sherwood Rowland, right, and Mario Molina in their laboratory at the University of California in 1976. Photograph AP

In a scientific paper published in Nature in June 1974, University of California researchers Sherwood Rowland and Mario Molina suggested that CFCs – a group of human-made industrial chemicals – could destroy ozone when they reach the upper atmosphere. But that received little attention outside specialist circles.

So Rowland and Molina decided to go public. They held an impromptu press conference at a scientific meeting a few months later. When the media covered their findings, the public became aware of the potential threat for the first time.

Public concern, in turn, prompted policy makers to act. The US government passed amendments to the Clean Air Act in 1977 that called for the regulation of any substance “reasonably anticipated to affect the stratosphere.”

Soon afterwards, the use of CFCs as propellants in spray cans was banned in the US, Canada and Scandinavian countries. Chemical companies – which had tried rearguard action for a while — began to seek alternatives.

The turning point came later that year, when British scientist Joe Farman observed a seasonal thinning of ozone over the Antarctica. This discovery of the ‘ozone hole’ created news headlines and galvanised international action that culminated in Montreal two years later.

This is a prime example of how good science, well covered by the media, led to specific and sustained action. As British science writer and TV producer Robert Lamb (1952-2012), one of my mentors, noted in 2002: “If an advertising agency had been responsible for attracting public attention to the ozone issue to force the hand of governments, it would have won every accolade in the business. But even the best agency in the world could not have invented the ozone hole, which triggered an avalanche of public concern.”

Antarctic Ozone Hole over the years

The Montreal Protocol blazed new trails on several fronts. It was the first legally binding international environment agreement to adopt the “precautionary principle” of setting out a strategy for immediate action even before all of the scientific ramifications are understood.

It also differentiated between the developed and developing countries in recognising the origins of the problem and in distributing responsibility for solving it. This principle is now prominent in climate treaty talks as well, albeit with far less consensus…

In some respects, this ozone treaty has yielded more climate benefits than the climate treaty itself — even if only as a by-product. The Kyoto Protocol adopted in 1997, in contrast, is mired in political bickering and struggling to meet targets.

Double Benefits

The reason for this is an atmospheric coincidence. Some ozone damaging chemicals also happen to be powerful greenhouse gases that trap the Sun’s heat and warm up the atmosphere. So getting rid of them protects the ozone layer and also mitigates climate change.

For example, CFC-12 has a global warming potential 12,000 times higher than Carbon Dioxide – the best known culprit of climate change.

By eliminating CFCs by 2009, the Montreal Protocol automatically removed 8 giga tons of global warming gases from the atmosphere — roughly equal to Carbon Dioxide emissions by 55 million cars running for 30 years.

Recent calculations suggest that the Montreal Protocol has probably (and unintentionally) helped delay global warming by seven to 12 years – a helpful ‘grace period’ in which to work out climate protection strategies.

The ozone and climate treaties originated and evolved separately, each addressing a specific atmospheric problem caused by human activity. It took nearly two decades for everyone involved to realise their common ground — or, in this case, the common air!

“We have phased out 98% of ozone depleting substances and also avoided an estimated 135 giga tons of CO2 equivalent emissions of those substances,” says Marco Gonzalez, Executive Secretary of the UN Environment Programme’s Ozone Secretariat. “Our actions over the past quarter century have helped usher in an Ozone-Safe Generation. This is truly worthy of celebration!”

Accolades have been coming for a while. Three scientists – Paul Crutzen, Sherwood Rowland and Mario Molina – shared the 1995 Nobel Prize for chemistry for their eventually life-saving work in the mid 1970s.

Rowland — once vilified by some chemical companies as a ‘KGB agent’ out to wreck American industry — lived to see the far reaching impacts of his most important research. He passed away in March this year, aged 84.

We salute him, and all others who made the skies safer again.

The Antarctic Ozone Hole — From Discovery to Recovery, a Scientific Journey

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About Nalaka Gunawardene

A science writer by training, I've worked as a journalist and communication specialist across Asia for 25+ years. During this time, I have variously been a news reporter, feature writer, radio presenter, TV quizmaster, documentary film producer, foreign correspondent and journalist trainer. I continue to juggle some of these roles, while also blogging and tweeting and column writing.
There's NOTHING OFFICIAL about this blog. In fact, there's NOTHING OFFICIAL about me! I've always stayed well clear of ALL centres of power and authority.